CVE-2025-39917

/// Technical description

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

bpf: Fix out-of-bounds dynptr write in bpf_crypto_crypt

Stanislav reported that in bpf_crypto_crypt() the destination dynptr's

size is not validated to be at least as large as the source dynptr's

size before calling into the crypto backend with 'len = src_len'. This

can result in an OOB write when the destination is smaller than the

source.

Concretely, in mentioned function, psrc and pdst are both linear

buffers fetched from each dynptr:

psrc = __bpf_dynptr_data(src, src_len);

[...]

pdst = __bpf_dynptr_data_rw(dst, dst_len);

[...]

err = decrypt ?

ctx->type->decrypt(ctx->tfm, psrc, pdst, src_len, piv) :

ctx->type->encrypt(ctx->tfm, psrc, pdst, src_len, piv);

The crypto backend expects pdst to be large enough with a src_len length

that can be written. Add an additional src_len > dst_len check and bail

out if it's the case. Note that these kfuncs are accessible under root

privileges only.

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References