CVE-2026-66337

MEDIUMPre-NVD 6.56.5
EchelonGraph scoreMEDIUM confidence

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

Score 6.5 from GitHub Security Advisory published 2026-07-25. A secondary CVSS source baseline 6.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: EPSS, GitHub Security Advisory, a secondary CVSS source
6.5EG
EchelonGraph verdictMonitorRemediate within your standard update timelines at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.2%CVSS: 6.5Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

A flaw was found in libsoup. An unsigned integer underflow in the soup_filter_input_stream_read_until() function causes a heap buffer over-read when parsing multipart HTTP responses. A malicious HTTP server can exploit this by sending a crafted multipart response, potentially causing the client application to crash or disclose sensitive heap memory.

CVSS v3
6.5
EG Score
6.5MEDIUMmedium confidence
EG Risk
44
EG Risk 44/100

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)
Severity65% × 45%
Impact severity (EG Severity): CVSS 6.5 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.2% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability100% × 15%
CISA's SSVC Automatable value: yes (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Attend at high (mission-essential systems).
Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (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 at low or medium mission impact and sooner than that at high.
EPSS PROB
0.2%
EPSS %ILE
14th
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 (6.5): severity, escalated by confirmed exploitation. This CVE's 6.5 is its impact severity (EG Severity), not escalated.

EG Severity
6.5 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood
0.2% 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; Attend at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; 60 days 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; Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (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; 60 days if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact partial (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

July 24, 2026

Last Modified

August 24, 2026

Advisory Details (2)

Auto-updated Jul 25, 2026
Patch available. Sources: redhat.
Red Hat

2506949 – (CVE-2026-66337) CVE-2026-66337 libsoup: libsoup: Heap buffer over-read via integer underflow in soup_filter_input_stream_read_until()

https://bugzilla.redhat.com/show_bug.cgi?id=2506949
Red HatMentions a patch (unverified)

cve-details

https://access.redhat.com/security/cve/CVE-2026-66337

Vendor Advisories for CVE-2026-66337(2)

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

Affected Packages

(6 across 4 ecosystems)
Debian:12(2)
PackageVulnerable rangeFix by version rangeDependents
libsoup2.42.74.3-1 ... 2.74.3-9 (16 versions)
  • every version on: no fix on record
—
libsoup33.2.2-2 ... 3.6.6-1 (35 versions)
  • every version on: no fix on record
—
Debian:13(2)
PackageVulnerable rangeFix by version rangeDependents
libsoup2.42.74.3-10.1, 2.74.3-11
  • every version on: no fix on record
—
libsoup33.6.5-3 ... 3.6.6-1 (8 versions)
  • every version on: no fix on record
—
Debian:11(1)
PackageVulnerable rangeFix by version rangeDependents
libsoup2.42.72.0-2 ... 2.74.3-9 (28 versions)
  • every version on: no fix on record
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
libsoup33.6.5-3 ... 3.6.6-1 (8 versions)
  • every version on: no fix on record
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 8× in last 7d / 48× 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 100 of 200 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. None are among the latest 100 rows. The 100 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  2. 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  3. 2026-10-18 03:21 UTCEG score recompute
  4. 2026-10-17 16:35 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  5. 2026-10-16 16:43 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  6. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  7. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  8. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  9. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  10. 2026-10-12 15:46 UTCEG score recompute
  11. 2026-10-11 19:31 UTCEG score recompute
  12. 2026-10-11 16:46 UTCEG score recompute
  13. 2026-10-11 14:07 UTCEG score recompute
  14. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  15. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  16. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  17. 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  18. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  19. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  20. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  21. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  22. 2026-10-04 07:41 UTCEG score recompute
  23. 2026-10-04 07:41 UTCVendor advisory
  24. 2026-10-04 07:41 UTCGHSA enrichmentGHSA-ww4c-c3rv-f96h · GitHub CVSS 6.5
  25. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.4% · 30th percentile
Show 75 more
  1. 2026-10-02 19:42 UTCEG score recompute
  2. 2026-10-02 19:42 UTCVendor advisory
  3. 2026-10-02 19:42 UTCGHSA enrichmentGHSA-ww4c-c3rv-f96h · GitHub CVSS 6.5
  4. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  5. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  6. 2026-10-01 04:31 UTCEG score recompute
  7. 2026-10-01 04:31 UTCVendor advisory
  8. 2026-10-01 04:31 UTCGHSA enrichmentGHSA-ww4c-c3rv-f96h · GitHub CVSS 6.5
  9. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  10. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  11. 2026-09-28 04:25 UTCEG score recompute
  12. 2026-09-28 04:25 UTCVendor advisory
  13. 2026-09-28 04:25 UTCGHSA enrichmentGHSA-ww4c-c3rv-f96h · GitHub CVSS 6.5
  14. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  15. 2026-09-25 09:59 UTCEG score recompute
  16. 2026-09-25 09:59 UTCGHSA enrichmentGHSA-ww4c-c3rv-f96h · GitHub CVSS 6.5
  17. 2026-09-23 22:16 UTCEG score recompute
  18. 2026-09-23 22:16 UTCVendor advisory
  19. 2026-09-23 22:16 UTCGHSA enrichmentGHSA-ww4c-c3rv-f96h · GitHub CVSS 6.5
  20. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  21. 2026-09-22 22:09 UTCEG score recompute
  22. 2026-09-22 22:08 UTCGHSA enrichmentGHSA-ww4c-c3rv-f96h · GitHub CVSS 6.5
  23. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  24. 2026-09-20 01:39 UTCEG score recompute
  25. 2026-09-20 01:39 UTCGHSA enrichmentGHSA-ww4c-c3rv-f96h · GitHub CVSS 6.5
  26. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  27. 2026-09-18 08:39 UTCEG score recompute
  28. 2026-09-18 08:39 UTCGHSA enrichmentGHSA-ww4c-c3rv-f96h · GitHub CVSS 6.5
  29. 2026-09-17 10:08 UTCEG score recompute
  30. 2026-09-17 10:08 UTCGHSA enrichmentGHSA-ww4c-c3rv-f96h · GitHub CVSS 6.5
  31. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  32. 2026-09-16 11:58 UTCEG score recompute
  33. 2026-09-16 11:58 UTCGHSA enrichmentGHSA-ww4c-c3rv-f96h · GitHub CVSS 6.5
  34. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  35. 2026-09-15 09:33 UTCEG score recompute
  36. 2026-09-15 09:33 UTCGHSA enrichmentGHSA-ww4c-c3rv-f96h · GitHub CVSS 6.5
  37. 2026-09-14 11:03 UTCEG score recompute
  38. 2026-09-14 11:03 UTCGHSA enrichmentGHSA-ww4c-c3rv-f96h · GitHub CVSS 6.5
  39. 2026-09-13 12:53 UTCEG score recompute
  40. 2026-09-13 12:53 UTCGHSA enrichmentGHSA-ww4c-c3rv-f96h · GitHub CVSS 6.5
  41. 2026-09-12 14:44 UTCGHSA enrichmentGHSA-ww4c-c3rv-f96h · GitHub CVSS 6.5
  42. 2026-09-11 16:34 UTCEG score recompute
  43. 2026-09-11 16:34 UTCGHSA enrichmentGHSA-ww4c-c3rv-f96h · GitHub CVSS 6.5
  44. 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  45. 2026-09-11 09:37 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  46. 2026-09-10 13:33 UTCEG score recompute
  47. 2026-09-10 13:33 UTCGHSA enrichmentGHSA-ww4c-c3rv-f96h · GitHub CVSS 6.5
  48. 2026-09-09 08:42 UTCEG score recompute
  49. 2026-09-09 08:42 UTCGHSA enrichmentGHSA-ww4c-c3rv-f96h · GitHub CVSS 6.5
  50. 2026-09-08 22:01 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  51. 2026-09-07 21:23 UTCGHSA enrichmentGHSA-ww4c-c3rv-f96h · GitHub CVSS 6.5
  52. 2026-09-06 17:32 UTCEG score recompute
  53. 2026-09-06 17:32 UTCGHSA enrichmentGHSA-ww4c-c3rv-f96h · GitHub CVSS 6.5
  54. 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  55. 2026-09-05 19:22 UTCEG score recompute
  56. 2026-09-05 19:22 UTCGHSA enrichmentGHSA-ww4c-c3rv-f96h · GitHub CVSS 6.5
  57. 2026-09-05 15:31 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  58. 2026-09-04 12:44 UTCEG score recompute
  59. 2026-09-04 12:43 UTCGHSA enrichmentGHSA-ww4c-c3rv-f96h · GitHub CVSS 6.5
  60. 2026-09-04 05:07 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  61. 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  62. 2026-09-01 23:15 UTCEG score recompute
  63. 2026-09-01 23:15 UTCGHSA enrichmentGHSA-ww4c-c3rv-f96h · GitHub CVSS 6.5
  64. 2026-09-01 13:54 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  65. 2026-09-01 04:40 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  66. 2026-08-30 22:23 UTCEG score recompute
  67. 2026-08-30 22:23 UTCGHSA enrichmentGHSA-ww4c-c3rv-f96h · GitHub CVSS 6.5
  68. 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  69. 2026-08-30 01:22 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  70. 2026-08-30 00:14 UTCEG score recompute
  71. 2026-08-30 00:14 UTCGHSA enrichmentGHSA-ww4c-c3rv-f96h · GitHub CVSS 6.5
  72. 2026-08-28 21:42 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  73. 2026-08-27 11:49 UTCEG score recompute
  74. 2026-08-27 11:49 UTCGHSA enrichmentGHSA-ww4c-c3rv-f96h · GitHub CVSS 6.5
  75. 2026-08-26 14:47 UTCEPSS rescoreEPSS 0.2% · 13th percentile

Frequently asked(5)

What is CVE-2026-66337?
CVE-2026-66337 is a medium-severity vulnerability; its CVE record was published on July 24, 2026. A flaw was found in libsoup. An unsigned integer underflow in the soupfilterinputstreamread_until() function causes a heap buffer over-read when parsing multipart HTTP responses. A malicious HTTP server can exploit this by sending a crafted multipart response, potentially causing the client…
When was CVE-2026-66337 made public?
CVE-2026-66337 was made public on June 5, 2026: that is the date its CVE record's CNA, Red Hat, Inc., gives for when the vulnerability was made public. The CVE record itself was published on July 24, 2026. EchelonGraph's copy of the record carries a last-modified date of August 24, 2026; the record at its source may have been updated since.
Is CVE-2026-66337 actively exploited?
CVE-2026-66337 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.2% probability of exploitation in the next 30 days (14th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-66337?
CVE-2026-66337 has a CVSS base score of 6.5 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-66337?
A fix for CVE-2026-66337 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-66337 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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