n0k0 has uploaded a new patch set (#3). ( https://gerrit.osmocom.org/c/osmo-ggsn/+/42885?usp=email )

Change subject: gtp: fix OOB write in PDP ctx GSN-Address decode ......................................................................

gtp: fix OOB write in PDP ctx GSN-Address decode

gtp_decode_pdp_ctx() takes the GSN-Address sub-field lengths of a PDP Context IE (gsnrc / gsnru, the GGSN control- and user-plane addresses) straight from the wire and memcpy()s that many bytes into the fixed 16-byte 'struct ul16_t' v[] array, with no check against the destination size. decode_pdp_ctx_len_check() only validates the declared lengths against the *input* buffer, never against the destination capacity, so a wire length of 17..255 overflows the 16-byte field by up to 239 bytes, clobbering adjacent struct pdp_t state.

The PDP Context IE is carried in SGSN Context Response / Forward Relocation messages exchanged between peer GSNs over Gn/Gp, so a malicious or spoofed peer GSN can trigger this. The same libgtp decoder is linked by osmo-sgsn, so it is affected as well.

A GSN address is 4 (IPv4) or 16 (IPv6) bytes, so reject any length that does not fit the destination before copying.

This issue has been assigned the CVE candidate identifier CAN-2026-2051035.

Change-Id: Id69e82fe1a16933d8c6b9c848a2ede29f7920d98 --- M gtp/gtp.c 1 file changed, 12 insertions(+), 0 deletions(-)

git pull ssh://gerrit.osmocom.org:29418/osmo-ggsn refs/changes/85/42885/3