AI analysis
A stack-based buffer overflow (CWE-121) exists in the tdelete function of the GNU C Library versions 2.1 through 2.44, where two rebalancing branches push an entry onto an internal parent-node stack without checking capacity, writing one pointer past the end of an alloca-allocated array. Triggering it requires deleting a node at a depth of exactly 40 (or 40 plus a multiple of 20), which implies a tree of at least a million nodes, meaning an attacker would need to drive a very large number of insertions and deletions through an application that uses tsearch/tdelete. The written value is a pointer into a tree node and is not directly attacker controlled, so the most likely outcome is an application crash (low confidentiality/integrity/availability impact per the CVSS 5.6 rating). No affected application in common Linux distributions has been identified, significantly limiting real-world attack surface. No public proof of concept exists and the flaw is not in the CISA KEV catalog.
What to do: Apply distribution security updates for glibc as they ship (Ubuntu has published USN-8737-1 and USN-8737-2 covering this issue) rather than waiting for a targeted exploit. Audit any in-house or third-party applications that use tsearch/tdelete on attacker-influenced data, and confirm they cannot accumulate trees of a million or more nodes. Because the written value is not attacker controlled, the primary risk is denial of service via crash, so prioritize patching on long-running services that maintain large search trees.
Affected
| GNU Project GNU C Library (glibc) | 2.1 through 2.44 |
Estimated exposure
masshundreds of millions of Linux systems (glibc ships as the default C library on nearly all major distributions), though realistically exploitable applications… — glibc is the standard C runtime on virtually every mainstream Linux distribution, so nearly every Linux host carries the vulnerable code, but the million-node tree requirement means the set of applications where it can plausibly be…
Order-of-magnitude estimate by the model from install counts, market share and public scan data it knows; verify before quoting.
Description
Calling tdelete on a sufficiently deep tree in the GNU C Library version 2.1 to 2.44 may write one pointer past the end of an alloca-allocated array on the stack, which may crash the application. The tdelete implementation keeps an explicit stack of parent nodes for rebalancing, which is grown as needed while descending the tree. Two rebalancing branches push an additional entry without checking the capacity, and write past the array when the stack is exactly full. Triggering this requires a node at a depth of exactly 40 (or 40 plus a multiple of 20), which implies a tree with at least a million nodes, so an attacker must drive a large number of insertions and deletions through an application that uses tsearch and tdelete. The written value is a pointer into a tree node and is not directly attacker controlled. No affected application in common distributions has been identified.