Bug 2571751 (CVE-2026-100290)

Summary: CVE-2026-100290 glibc: glibc: Denial of Service via memory allocation failure during regular expression processing
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: low Docs Contact:
Priority: low    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, ashankar, codonell, dj, dpaolell, fweimer, jdelft, jupierce, lgarciaa, mbiarnes, pfrankli, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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A flaw was found in glibc. When an application compiles or matches regular expressions under system memory pressure, memory allocation failures can cause internal memory tracking errors, leading to accessing or releasing memory blocks that have already been freed. An attacker who provides regular expressions or target strings to an affected application could trigger this flaw, resulting in an application crash and a denial of service (DoS).
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Description OSIDB Bzimport 2026-11-11 16:11:10 UTC 
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.