vulnerability / NVI-00015396 / Revision 1
re2: Out-of-bounds heap read in `exec`/`test`/`match` via attacker-influenced `lastIndex` on a non-ASCII subject → uncatchable process crash (DoS)
GitHub lists this reviewed advisory for re2. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
5.7 medium
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
re2
source listed<= 1.25.1
## Summary `re2` validates the user-settable `lastIndex` against the subject's **UTF-8 byte length** but then uses it as a **UTF-16 code-unit count** to walk the subject buffer, with no bounds check. For any non-ASCII subject, the byte length is larger than the true character count, so a `lastIndex` between those two values passes validation while pointing past the end of the buffer. The subsequent walk reads out of bounds. With a large subject the read marches into unmapped memory and the process dies with **SIGABRT/SIGSEGV** — an uncatchable crash (`try/catch` cannot stop it), i.e. a denial of service for any worker/process that runs the match. In some cases the out-of-bounds bytes are copied into the returned value (a bounded, best-effort heap information leak). ## Root cause The subject wrapper stores the UTF-8 **byte** length in `StrVal::length`: - `lib/addon.cc:200` `auto argLength = utf8Length(s, isolate);` — UTF-8 **byte** count - `lib/addon.cc:209` `lastStringValue.reset(buffer, argSize, argLength, startFrom, false, isAscii);` `setIndex` then validates the (UTF-16) `lastIndex` against that byte length and walks the buffer by character count: ```cpp // lib/addon.cc:22
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
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- GHSA-ff84-5f28-78qj ↗
GitHub Advisory Database · vendor advisory
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Public revision history
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- Revision 1 ·
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