CVE-2026-9256: NGINX ngx_http_rewrite_module vulnerability
- Is it exploited?
Not on CISA's list. CISA has not added it to the Known Exploited Vulnerabilities catalog as of . If CISA adds it, this page shows it as known exploited.
- How likely is exploitation in the next 30 days?
- 10.9%
EPSS score, percentile 95.8 of all scored records. A probability estimated by FIRST, not a report of exploitation.
- How severe?
- 9.2 Critical
CVSS v4.0 base score, given by the CNA
- What should I do?
CISA has set no required action, because the vulnerability is not in KEV.
- Which versions are affected?
Affected
- from 37.0 to before 37.0.1.1
- from R36 to before R36 P5
- from R32 to before R32 P7
- from 1.31.0 to before 1.31.1
- from 1.30.0 to before 1.30.2
- 0.1.17 through 0.9.7
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of ; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of ; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of . About the data.
What to do
Advisories and patches
Affected products and versions
As listed in the CVE record.
| Status | Versions |
|---|---|
| Affected | from 37.0 to before 37.0.1.1 |
| Affected | from R36 to before R36 P5 |
| Affected | from R32 to before R32 P7 |
Versions not listed are: unknown.
| Status | Versions |
|---|---|
| Affected | from 1.31.0 to before 1.31.1 |
| Affected | from 1.30.0 to before 1.30.2 |
| Affected | 0.1.17 through 0.9.7 |
Versions not listed are: unaffected.
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of . About the data.
About this vulnerability
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$2) in a redirect or arguments context. An unauthen…
Summary: CVE record, as of .
- CISA has not added CVE-2026-9256 to its Known Exploited Vulnerabilities (KEV) catalog, as of 28 Oct 2026.
- The CVE record was published on 22 May 2026.
- The CVE record carries a CVSS v4.0 base score of 9.2 (Critical), given by its CNA.
- FIRST's EPSS model puts the probability of exploitation in the next 30 days at 10.9% (percentile 95.8), as of 28 Oct 2026. EPSS is a statistical estimate, not a report of exploitation.
- CISA's SSVC assessment in the CVE record: exploitation none, automatable no, technical impact total.
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of ; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of ; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of . About the data.
Description
NGINX ngx_http_rewrite_module vulnerability
NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_rewrite_module module. This vulnerability exists when a rewrite directive uses a regex pattern with distinct, overlapping Perl-Compatible Regular Expression (PCRE) captures (for example, ^/((.*))$) 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.
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of . About the data.
Weakness
- CWE-122: Heap-based Buffer Overflow
CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record.
Timeline
| Date | Event |
|---|---|
| CVE record published | |
| CVE record last updated |
Known exploited F5 vulnerabilities
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