CVE-2026-9256

HIGHPre-NVD 8.18.1—
EchelonGraph scoreMEDIUM confidence

Score 8.1 from GitHub Security Advisory (severity: CRITICAL) published 2026-05-26. a secondary CVSS source baseline 8.1; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Elevated
8.1EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 10%CVSS: 8.1Exploit: Elevated riskExposed: 0

A fix is available — apply it.

NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_rewrite_module module. This vulnerability exists when a rewrite directive uses a regex pattern with distinct, overlapping Perl-Compatible Regular Expression (PCRE) captures (for example, ^/((.*))$) and a replacement string that references multiple such captures (for example, $1$2) in a redirect or arguments context. An unauthenticated attacker along with conditions beyond their control can exploit this vulnerability by sending crafted HTTP requests. This may cause a heap buffer overflow in the NGINX worker process leading to a restart. Additionally, attackers can execute code on systems with Address Space Layout Randomization (ASLR) disabled or when the attacker can bypass ASLR.

Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

CVSS v3
8.1
EG Score
8.1(medium)
EG Risk
52(Track)
EG Risk 52/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity81% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
10%
EPSS %ILE
95%
KEV
Not listed

Published

May 22, 2026

Last Modified

August 25, 2026

Advisory Details (1)

Auto-updated May 28, 2026
No patch confirmed yet.
generic

myF5

https://my.f5.com/manage/s/article/K000161377

Vendor Advisories for CVE-2026-9256(10)

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

Patch Availability(11)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntunginx-light (1.28.3-2ubuntu1.2) @ resolute2026-08-25ubuntu
ubuntunginx-light (1.18.0-0ubuntu1.7+esm1) @ focal2026-08-25ubuntu
redhatrhui5/rhua-tp-rhel9:17872412602026-08-24redhat
redhatrhui5/rhua-rhel9:17847950762026-07-23redhat
redhatdiscovery/discovery-ui-rhel9:17827565412026-06-29redhat
redhatnginx:1.26-9080020260609152155.92026-06-25redhat
redhatnginx-2:1.26.3-6.el10_2.42026-06-25redhat
redhatnginx-2:1.20.1-28.el9_8.32026-06-24redhat
redhatnginx:1.24-8100020260611094050.489197e62026-06-24redhat
redhatnginx:1.24-9080020260610161820.92026-06-23redhat
redhatnginx-main-1.30.2-1.hum12026-05-23redhat

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

(8 across 8 ecosystems)
Alpine:v3.21(1)
PackageVulnerable rangeFixed inDependents
nginx—1.26.3-r1—
Alpine:v3.22(1)
PackageVulnerable rangeFixed inDependents
nginx—1.28.3-r2—
Alpine:v3.23(1)
PackageVulnerable rangeFixed inDependents
nginx—1.28.3-r2—
Alpine:v3.24(1)
PackageVulnerable rangeFixed inDependents
nginx—1.30.2-r0—
Debian:11(1)
PackageVulnerable rangeFixed inDependents
nginx1.18.0-6.1 ... 1.18.0-6.1+deb11u6 (7 versions)1.18.0-6.1+deb11u7—
Debian:12(1)
PackageVulnerable rangeFixed inDependents
nginx1.22.1-9 ... 1.22.1-9+deb12u7 (8 versions)1.22.1-9+deb12u8—
Debian:13(1)
PackageVulnerable rangeFixed inDependents
nginx1.26.3-3 ... 1.26.3-3+deb13u5 (6 versions)1.26.3-3+deb13u6—
Debian:14(1)
PackageVulnerable rangeFixed inDependents
nginx1.26.3-3 ... 1.30.1-2 (22 versions)1.30.1-3—

Weakness Classification(1)

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

Additional Vendor Advisories

(3)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 6× in last 7d / 94× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. 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. Most recent first.

Showing the most recent 100 of 271 total refreshes for this CVE.

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

Publicly available exploits

(3 references)

Working exploit code is in the public domain (3 GitHub PoCs). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • GitHub PoCy198nt/Nginx-chain-Rift-Poolslip
    First seen Jun 5, 2026

    Nginx RCE chain PoC with CVE-2026-9256 and CVE-2026-42945

    Open source ↗
  • GitHub PoC3nou9h/CVE-2026-9256-Poc
    First seen May 28, 2026
    Open source ↗
  • GitHub PoCW5M1n9/NGINX-ngx_http_rewrite_module-heap-buffer-overflow-CVE-2026-9256
    First seen May 28, 2026
    Open source ↗

Frequently asked(5)

What is CVE-2026-9256?
CVE-2026-9256 is a high vulnerability published on May 22, 2026. NGINX Plus and NGINX Open Source have a vulnerability in the ngxhttprewrite_module module. This vulnerability exists when a rewrite directive uses a regex pattern with distinct, overlapping Perl-Compatible Regular Expression (PCRE) captures (for example, ^/((.*))$) and a replacement string that…
When was CVE-2026-9256 disclosed?
CVE-2026-9256 was first published in the National Vulnerability Database on May 22, 2026, with the most recent update on August 25, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-9256 actively exploited?
CVE-2026-9256 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 10% probability of exploitation in the next 30 days, which ranks it in the top 4.7% of all scored CVEs.
What is the CVSS score of CVE-2026-9256?
CVE-2026-9256 has a CVSS v3 base score of 8.1 (NVD).
How do I remediate CVE-2026-9256?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-9256, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-9256

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