Buffer overflow in F5 Dos

CVE-2026-42945

NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_rewrite_module module. This vulnerability exists when the rewrite directive is followed by a rewrite, if, or set directive and an unnamed Perl-Compatible Regular Expression (PCRE) capture (for example, $1, $2) with a replacement string that includes a question mark (?). An unauthenticated attacker along with conditions beyond its 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.

Vulnerability class: Buffer Overflow

Published · last modified .

CVSS v3 metric

CVSS v3 base score 8.1 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.034 (88.7th percentile), scored .

Low probability of exploitation in the next 30 days, but still tracked. 89th percentile — 88.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-42945: fell from 0.680 to 0.034.

EPSS over last 30 days · oldest: 0.680 · newest: 0.034 · change: -0.647

Affected products

Weakness classification (CWE)

Public proof-of-concept exploits

References

Frequently asked questions

What is CVE-2026-42945?
CVE-2026-42945 is a high-severity vulnerability in F5 Dos, classified under Heap-based Buffer Overflow. CVSS score: 8.1/10. Published 2026-05-13.
How severe is CVE-2026-42945?
High severity. CVSS v3 base score is 8.1 out of 10.
Is CVE-2026-42945 known to be exploited?
57 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.