CVE-2025-39931

In the Linux kernel, the following vulnerability has been resolved:

crypto: af_alg - Set merge to zero early in af_alg_sendmsg

If an error causes af_alg_sendmsg to abort, ctx->merge may contain a garbage value from the previous loop. This may then trigger a crash on the next entry into af_alg_sendmsg when it attempts to do a merge that can't be done.

Fix this by setting ctx->merge to zero near the start of the loop.

The patch fixes a use of an uninitialized ctx->merge field in af_alg_sendmsg(). If a previous iteration aborted early, the next call could reuse a stale merge flag, causing the kernel to attempt merging data across invalid buffers, leading to crashes or memory corruption.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.