CVE
Double free after allocation failure in regcomp and regexec
- Exploited
- No known exploitation
- Fix
- See vendor advisory
- Who is exposed
- Not reported
- Last modified
- Whether it needs action now or is a reference record, by fixed rules, with why. Last checked is when cve.now last re-read it.What do these mean? →
- Reference
- Last checked
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 46/100 · provisional
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
The GNU C Library (glibc) `regcomp` and `regexec` functions can read freed memory and free the same memory block twice when a memory allocation fails during regular expression compilation or matching. An attacker can reach this remotely, without logging in, by supplying a pattern or subject string, and the expected result is a crash of the process, though the failure only occurs under memory pressure.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
Read the original description
The regcomp and regexec functions in the GNU C Library version 2.3 to version 2.44 may read freed memory and free the same heap block twice when a memory allocation fails while a regular expression is compiled or matched. The re_dfa_add_node (the NFA node table) and build_range_exp (bracket ranges) grow several arrays with consecutive realloc calls and store the new pointers only after all of them succeed. When a later call fails, the pattern buffer keeps pointers to blocks that were already freed, and the error cleanup frees them again. In regexec, the back-reference cache (match_ctx_add_entry) frees its array when a realloc fails but keeps the pointer, which is freed again on the error path.
An attacker does not need to supply a crafted regular expression: patterns large enough to grow these arrays are common. The failure has to hit a specific allocation, though, so the issue can only be reached when the system is already under memory pressure. An attacker who supplies the pattern or the subject string has little control over which allocation fails, so the expected impact is a crash of the process. This issue affects all architectures and ABIs supported by the GNU C Library.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure17/25No login or user action needed per the CVSS vector, reachable over the network without a login · Unknown: No advisory context yet
- Reach20/20Affects glibc (software on nearly every server, desktop or phone)
- Severity3.7/10CVSS 3.7
- No patch5/5No fixed version listed; see vendor advisory
What would change the score
- Would score about 91 if added to CISA KEV
- Would score about 86 if CISA's SSVC rates exploitation active
- Would score about 51 if advisories confirm default setups are exposed
Check your systems with an agent
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Check whether my systems are affected by CVE-2026-100290 (Double free after allocation failure in regcomp and regexec), using the cve.now data below.
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What cve.now has for CVE-2026-100290 (entry last updated 2026-11-11):
Affected:
- The GNU C Library glibc: from 2.3, through 2.44
Fixed versions: none listed yet.
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
CISA KEV: CVE-2026-100290 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-100290 only. If you also check another CVE, look up its own KEV status; never assume it from this one.
How to check:
- Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory.
Verify against the linked advisories before concluding, and cite the date you read each one:
- https://sourceware.org/git/?p=glibc.git;a=blob_plain;f=advisories/GLIBC-SA-2026-0028
- https://sourceware.org/bugzilla/show_bug.cgi?id=34991
- https://sourceware.org/bugzilla/show_bug.cgi?id=31935
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.
Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.
Entry: https://cve.now/CVE-2026-100290
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "CVE-2026-100290"}.Timeline
- CVE published
- First seen by cve.now
Affected versions
- The GNU C Library glibc
From 2.3 · through 2.44
Evidence 5
CVE record · 2
Establishes: The identifier and description.
- Record
- Record
Write-ups · 2
Establishes: Technical detail and context.
- Report
- Report
Other links · 1
- Advisory
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-100290
Is CVE-2026-100290 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
Which versions are affected by CVE-2026-100290?
glibc: from 2.3 through 2.44.Source: cve.now feed data