laforge has submitted this change. ( https://gerrit.osmocom.org/c/osmo-ggsn/+/42885?usp=email )
(
3 is the latest approved patch-set. No files were changed between the latest approved patch-set and the submitted one. )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(-)
Approvals: Jenkins Builder: Verified pespin: Looks good to me, but someone else must approve fixeria: Looks good to me, approved
diff --git a/gtp/gtp.c b/gtp/gtp.c index 7a439d9..f378c17 100644 --- a/gtp/gtp.c +++ b/gtp/gtp.c @@ -1245,12 +1245,24 @@ /* GGSN Address Ctrl */ pdp->gsnrc.l = *ptr; ptr++; + if (pdp->gsnrc.l > sizeof(pdp->gsnrc.v)) { + LOGP(DLGTP, LOGL_ERROR, + "PDP Context Decode: GSN Address (Ctrl) length %u exceeds %zu\n", + pdp->gsnrc.l, sizeof(pdp->gsnrc.v)); + return -EINVAL; + } memcpy(pdp->gsnrc.v, ptr, pdp->gsnrc.l); ptr += pdp->gsnrc.l;
/* GGSN Address User */ pdp->gsnru.l = *ptr; ptr++; + if (pdp->gsnru.l > sizeof(pdp->gsnru.v)) { + LOGP(DLGTP, LOGL_ERROR, + "PDP Context Decode: GSN Address (User) length %u exceeds %zu\n", + pdp->gsnru.l, sizeof(pdp->gsnru.v)); + return -EINVAL; + } memcpy(pdp->gsnru.v, ptr, pdp->gsnru.l); ptr += pdp->gsnru.l;