CVE-2026-9256 (GCVE-0-2026-9256)

Vulnerability from cvelistv5 – Published: 2026-05-22 14:11 – Updated: 2026-07-15 00:38 X_F5
VLAI
Title
NGINX ngx_http_rewrite_module vulnerability
Summary
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.
Severity
8.1 (High)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
9.2 (Critical)
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
SSVC
Exploitation: none Automatable: no Technical Impact: total
CISA Coordinator (v2.0.3)
CWE
  • CWE-122 - Heap-based Buffer Overflow
Assigner
f5
References
Impacted products
Vendor Product Version
F5 NGINX Plus Affected: 37.0 , < 37.0.1.1 (custom)
Affected: R36 , < R36 P5 (custom)
Affected: R32 , < R32 P7 (custom)
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F5 NGINX Open Source Affected: 1.31.0 , < 1.31.1 (custom)
Affected: 1.30.0 , < 1.30.2 (custom)
Affected: 0.1.17 , ≤ 0.9.7 (custom)
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Red Hat Red Hat Enterprise Linux 10 Unaffected: 2:1.26.3-6.el10_2.4 , < * (rpm)
    cpe:/o:redhat:enterprise_linux:10.2
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Red Hat Red Hat Enterprise Linux 8 Unaffected: 8100020260611094050.489197e6 , < * (rpm)
    cpe:/a:redhat:enterprise_linux:8
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Red Hat Red Hat Enterprise Linux 9 Unaffected: 9080020260610161820.9 , < * (rpm)
    cpe:/a:redhat:enterprise_linux:9
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Red Hat Red Hat Enterprise Linux 9 Unaffected: 2:1.20.1-28.el9_8.3 , < * (rpm)
    cpe:/a:redhat:enterprise_linux:9
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Red Hat Red Hat Enterprise Linux 9 Unaffected: 9080020260609152155.9 , < * (rpm)
    cpe:/a:redhat:enterprise_linux:9
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Red Hat Red Hat Discovery 2 Unaffected: 1782756541 , < * (rpm)
    cpe:/a:redhat:discovery:2::el9
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Red Hat Red Hat Hardened Images Unaffected: 1.30.2-1.hum1 , < * (rpm)
    cpe:/a:redhat:hummingbird:1
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Red Hat Red Hat Lightspeed proxy 1     cpe:/a:redhat:insights_proxy:1
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Date Public
2026-05-22 14:00
Credits
"F5 acknowledges Mufeed VH of Winfunc Research, Nebula Security (@nebusecurity), and Vexera AI for bringing this issue to our attention and following the highest standards of coordinated disclosure."
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      "cveMetadata": "{\"cveId\": \"CVE-2026-9256\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-07-15T00:38:41.005Z\", \"dateReserved\": \"2026-05-21T20:58:58.484Z\", \"assignerOrgId\": \"9dacffd4-cb11-413f-8451-fbbfd4ddc0ab\", \"datePublished\": \"2026-05-22T14:11:41.877Z\", \"assignerShortName\": \"f5\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.