CVE-2026-40261

HIGHPre-NVD 8.88.8
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to the CVSS score beside it.

This high-severity CVE scores 8.8 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 1.9% (79th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from a secondary CVSS source
Sources: EPSS, a secondary CVSS source
Trending — 3 sources updated this weekElevated
8.8EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines (the SSVC decision on this page).
  • Public exploit or proof-of-concept code is available
CISA-KEV: Not listedEPSS PROB: 1.9%CVSS: 8.8Exploit: Public PoCExposed services: Not assessed

A fix is available — apply it.

Composer is a dependency manager for PHP. Versions 1.0 through 2.2.26 and 2.3 through 2.9.5 contain a command injection vulnerability in the Perforce::syncCodeBase() method, which appends the $sourceReference parameter to a shell command without proper escaping, and additionally in the Perforce::generateP4Command() method as in GHSA-wg36-wvj6-r67p / CVE-2026-40176, which interpolates user-supplied Perforce connection parameters (port, user, client) from the source url field without proper escaping. An attacker can inject arbitrary commands through crafted source reference or source url values containing shell metacharacters, even if Perforce is not installed. Unlike CVE-2026-40176, the source reference and url are provided as part of package metadata, meaning any compromised or malicious Composer repository can serve package metadata declaring perforce as a source type with malicious values. This vulnerability is exploitable when installing or updating dependencies from source, including the default behavior when installing dev-prefixed versions. This issue has been fixed in Composer 2.2.27 (2.2 LTS) and 2.9.6 (mainline). If developers are unable to immediately update, they can avoid installing dependencies from source by using --prefer-dist or the preferred-install: dist config setting, and only use trusted Composer repositories as a workaround.

CVSS v3
8.8
EG Score
8.8HIGHmedium confidence
EG Risk
56
EG Risk 56/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity88% × 45%
Impact severity (EG Severity): CVSS 8.8 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation40% × 40%
EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Track* at high (mission-essential systems).
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
1.9%
EPSS %ILE
79th
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (8.8): severity, escalated by confirmed exploitation. This CVE's 8.8 is its impact severity (EG Severity), not escalated.

EG Severity
8.8 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.a secondary CVSS source · CVSS v3.0 or v3.1
EG Likelihood
1.9% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-17). FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Track at medium mission impactTrack at low or medium mission impact; Track* at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Track* at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

April 15, 2026

Last Modified

July 15, 2026

Advisory Details (2)

Auto-updated May 2, 2026
Patch available. Sources: github.
GitHub advisoryMentions a patch (unverified)

Command injection via malicious Perforce source reference/url · Advisory · composer/composer · GitHub

https://github.com/composer/composer/security/advisories/GHSA-gqw4-4w2p-838q
Web page

Release 2.9.6 · composer/composer · GitHub

https://github.com/composer/composer/releases/tag/2.9.6

Vendor Advisories for CVE-2026-40261(2)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(1)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
redhatcomposer-main-2.9.7-1.hum12026-04-14redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(5 across 5 ecosystems)
Debian:11(1)
PackageVulnerable rangeFix by version rangeDependents
composer2.0.11-1 ... 2.9.8-1 (96 versions)
  • every version on: no fix on record
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
composer2.5.5-1, 2.5.5-1+deb12u1, 2.5.5-1+deb12u2, 2.5.5-1+deb12u3
  • every version up to 2.5.5-1+deb12u4: fixed in 2.5.5-1+deb12u4
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
composer2.8.8-1, 2.8.8-1+deb13u1
  • every version up to 2.8.8-1+deb13u2: fixed in 2.8.8-1+deb13u2
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
composer2.8.10-1 ... 2.9.5-1 (12 versions)
  • every version up to 2.9.7-1: fixed in 2.9.7-1
—
Packagist(1)
PackageVulnerable rangeFix by version rangeDependents
composer/composer1.0.0 ... 2.2.9 (147 versions)
  • 2.3.0 up to 2.9.6: fixed in 2.9.6
  • 1.0.0 up to 2.2.27: fixed in 2.2.27
—

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 10× in last 7d / 34× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

Showing the most recent 99 of 225 refreshes on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. 1 repeat row among the latest 100 is merged into the row it repeats. The 126 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-23 16:31 UTCEPSS rescoreEPSS 1.9% · 79th percentile
  2. 2026-10-22 16:34 UTCEPSS rescoreEPSS 1.9% · 79th percentile
  3. 2026-10-21 16:33 UTCEPSS rescoreEPSS 1.9% · 79th percentile
  4. 2026-10-20 16:33 UTCEPSS rescoreEPSS 1.9% · 79th percentile
  5. 2026-10-19 16:32 UTCEPSS rescoreEPSS 1.9% · 79th percentile
  6. 2026-10-18 16:32 UTCEPSS rescoreEPSS 1.9% · 79th percentile
  7. 2026-10-18 03:43 UTCEG score recompute
  8. 2026-10-17 16:34 UTCEPSS rescoreEPSS 1.9% · 79th percentile
  9. 2026-10-17 14:54 UTCEG score recompute
  10. 2026-10-17 14:54 UTCVendor advisory
  11. 2026-10-16 16:42 UTCEPSS rescoreEPSS 1.9% · 79th percentile
  12. 2026-10-15 16:32 UTCEPSS rescoreEPSS 1.9% · 79th percentile
  13. 2026-10-14 16:33 UTCEPSS rescoreEPSS 1.9% · 79th percentile
  14. 2026-10-13 16:34 UTCEPSS rescoreEPSS 1.9% · 79th percentile
  15. 2026-10-12 16:34 UTCEPSS rescoreEPSS 1.9% · 79th percentile
  16. 2026-10-12 16:09 UTCEG score recompute
  17. 2026-10-11 19:52 UTCEG score recompute
  18. 2026-10-11 17:05 UTCEG score recompute
  19. 2026-10-11 14:31 UTCEG score recompute
  20. 2026-10-11 13:48 UTCEPSS rescoreEPSS 1.9% · 79th percentile
  21. 2026-10-10 20:00 UTCEPSS rescoreEPSS 1.9% · 79th percentile
  22. 2026-10-10 19:33 UTCOSV refresh
  23. 2026-10-09 20:07 UTCEPSS rescoreEPSS 1.9% · 79th percentile
  24. 2026-10-08 17:12 UTCEPSS rescoreEPSS 1.9% · 79th percentile
  25. 2026-10-07 23:48 UTCEPSS rescoreEPSS 1.9% · 79th percentile
Show 74 more
  1. 2026-10-06 15:17 UTCEPSS rescoreEPSS 1.9% · 79th percentile
  2. 2026-10-05 17:43 UTCEPSS rescoreEPSS 1.9% · 79th percentile
  3. 2026-10-04 23:22 UTCEPSS rescoreEPSS 1.9% · 79th percentile
  4. 2026-10-03 14:25 UTCEPSS rescoreEPSS 1.9% · 79th percentile
  5. 2026-10-01 19:50 UTCEPSS rescoreEPSS 1.9% · 79th percentile
  6. 2026-09-30 15:03 UTCEPSS rescoreEPSS 1.9% · 79th percentile
  7. 2026-09-27 13:48 UTCEPSS rescoreEPSS 1.9% · 78th percentile
  8. 2026-09-26 15:58 UTCEPSS rescoreEPSS 1.9% · 78th percentile
  9. 2026-09-26 00:26 UTCEPSS rescoreEPSS 1.9% · 78th percentile
  10. 2026-09-21 06:49 UTCOSV refresh
  11. 2026-09-20 20:15 UTCEPSS rescoreEPSS 1.7% · 76th percentile
  12. 2026-09-18 19:28 UTCEPSS rescoreEPSS 1.7% · 75th percentile
  13. 2026-09-17 19:30 UTCEPSS rescoreEPSS 1.7% · 75th percentile
  14. 2026-09-16 14:08 UTCEPSS rescoreEPSS 1.7% · 75th percentile
  15. 2026-09-16 05:15 UTCEPSS rescoreEPSS 1.7% · 75th percentile
  16. 2026-09-15 03:11 UTCEPSS rescoreEPSS 1.7% · 75th percentile
  17. 2026-09-12 15:01 UTCEPSS rescoreEPSS 1.7% · 75th percentile
  18. 2026-09-11 14:53 UTCEPSS rescoreEPSS 1.7% · 75th percentile
  19. 2026-09-11 09:37 UTCEPSS rescoreEPSS 1.7% · 75th percentile
  20. 2026-09-10 09:34 UTCEPSS rescoreEPSS 1.7% · 75th percentile
  21. 2026-09-08 22:00 UTCEPSS rescoreEPSS 1.7% · 75th percentile
  22. 2026-09-07 16:01 UTCEPSS rescoreEPSS 1.7% · 75th percentile
  23. 2026-09-06 13:47 UTCEPSS rescoreEPSS 1.7% · 75th percentile
  24. 2026-09-04 05:06 UTCEPSS rescoreEPSS 1.7% · 75th percentile
  25. 2026-09-02 14:12 UTCEPSS rescoreEPSS 1.7% · 75th percentile
  26. 2026-09-02 04:58 UTCOSV refresh
  27. 2026-09-01 13:53 UTCEPSS rescoreEPSS 1.7% · 75th percentile
  28. 2026-09-01 04:39 UTCEPSS rescoreEPSS 1.7% · 75th percentile
  29. 2026-08-30 19:17 UTCEPSS rescoreEPSS 1.7% · 75th percentile
  30. 2026-08-30 01:22 UTCEPSS rescoreEPSS 1.7% · 75th percentile
  31. 2026-08-28 21:41 UTCEPSS rescoreEPSS 1.7% · 74th percentile
  32. 2026-08-27 14:25 UTCEPSS rescoreEPSS 1.7% · 75th percentile
  33. 2026-08-26 14:46 UTCEPSS rescoreEPSS 1.7% · 75th percentile
  34. 2026-08-25 13:49 UTCEPSS rescoreEPSS 1.7% · 75th percentile
  35. 2026-08-23 00:19 UTCEPSS rescoreEPSS 1.7% · 75th percentile
  36. 2026-08-21 23:49 UTCEPSS rescoreEPSS 1.7% · 75th percentile
  37. 2026-08-20 22:55 UTCEPSS rescoreEPSS 1.7% · 75th percentile
  38. 2026-08-19 17:03 UTCEPSS rescoreEPSS 1.7% · 75th percentile
  39. 2026-08-18 13:48 UTCEPSS rescoreEPSS 1.7% · 75th percentile
  40. 2026-08-17 13:47 UTCEPSS rescoreEPSS 1.7% · 75th percentile
  41. 2026-08-16 14:56 UTCEPSS rescoreEPSS 1.7% · 75th percentile
  42. 2026-08-16 06:37 UTCEG score recompute
  43. 2026-08-16 06:37 UTCVendor advisory
  44. 2026-08-16 02:14 UTCEPSS rescoreEPSS 1.7% · 75th percentile
  45. 2026-08-15 01:30 UTCEPSS rescoreEPSS 1.7% · 75th percentile
  46. 2026-08-14 16:06 UTCVendor advisory
  47. 2026-08-14 04:43 UTCEG score recompute
  48. 2026-08-14 04:43 UTCVendor advisory
  49. 2026-08-13 22:00 UTCEPSS rescoreEPSS 1.7% · 74th percentile
  50. 2026-08-13 08:56 UTCVendor advisory
  51. 2026-08-12 18:53 UTCEG score recompute
  52. 2026-08-12 18:53 UTCVendor advisory
  53. 2026-08-12 13:51 UTCEPSS rescoreEPSS 1.7% · 74th percentile
  54. 2026-08-11 17:04 UTCEG score recompute
  55. 2026-08-11 17:04 UTCVendor advisory
  56. 2026-08-11 13:43 UTCEPSS rescoreEPSS 1.7% · 74th percentile
  57. 2026-08-11 02:37 UTCEG score recompute
  58. 2026-08-11 02:37 UTCVendor advisory
  59. 2026-08-11 00:00 UTCEPSS rescoreEPSS 1.7% · 74th percentile
  60. 2026-08-10 02:46 UTCVendor advisory
  61. 2026-08-09 15:23 UTCEG score recompute
  62. 2026-08-09 15:23 UTCVendor advisory
  63. 2026-08-09 13:46 UTCEPSS rescoreEPSS 1.7% · 74th percentile
  64. 2026-08-09 03:59 UTCEG score recompute
  65. 2026-08-09 03:59 UTCVendor advisory
  66. 2026-08-08 16:37 UTCEPSS rescoreEPSS 1.7% · 74th percentile
  67. 2026-08-08 00:48 UTCEG score recompute
  68. 2026-08-08 00:48 UTCVendor advisory
  69. 2026-08-07 13:25 UTCEG score recompute
  70. 2026-08-07 13:25 UTCVendor advisory
  71. 2026-08-06 13:46 UTCEPSS rescoreEPSS 1.7% · 74th percentile
  72. 2026-08-06 12:06 UTCVendor advisory
  73. 2026-08-05 23:22 UTCEG score recompute
  74. 2026-08-05 23:22 UTCVendor advisory

Publicly available exploits

(1 reference)

Public exploit code is referenced for this CVE (1 GitHub PoC). Defenders should treat patch urgency accordingly.

  • GitHub PoCterminat0r7031/composer-CVE-2026-40261-CVE-2026-40176-PoC
    Published Apr 16, 2026
    Open source ↗

Related CVEs(same product + same vendor + same CWE)

Same vendor

2 shown

redhat:RHSA-2026:8165

Frequently asked(5)

What is CVE-2026-40261?
CVE-2026-40261 is a high-severity vulnerability; its CVE record was published on April 15, 2026. Composer is a dependency manager for PHP. Versions 1.0 through 2.2.26 and 2.3 through 2.9.5 contain a command injection vulnerability in the Perforce::syncCodeBase() method, which appends the $sourceReference parameter to a shell command without proper escaping, and additionally in the…
When was the CVE record for CVE-2026-40261 published?
The CVE record for CVE-2026-40261 was published on April 15, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of July 15, 2026; the record at its source may have been updated since.
Is CVE-2026-40261 actively exploited?
CVE-2026-40261 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1.9% probability of exploitation in the next 30 days (79th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-40261?
CVE-2026-40261 has a CVSS base score of 8.8 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-40261?
A fix for CVE-2026-40261 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-40261 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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