RUSTSEC-2026-0335 (GHSA-FWJG-CM92-J3HJ)
Vulnerability from osv_rustsec – Published: 2026-10-09 12:00 – Updated: 2026-10-12 08:58 – Source websitemykey implements MIKEY (RFC 3830) for SRTP key exchange. Pre-shared key mode
transmitted the TEK Generation Key (TGK) in the clear.
MikeyMessage::new_psk_init built its KEMAC payload with EncAlg::Null and
placed the TGK in enc_data verbatim. Anyone able to read a PSK-Init message
therefore recovers the TGK — and so the SRTP master key — without knowing the
pre-shared key.
The transmitted value was never even used by the receiver: complete_psk
re-derived the TGK from the pre-shared key and ignored enc_data entirely. The
field was write-only; it provided nothing and disclosed everything.
A second consequence: the message authentication key was derived from the TGK rather than from the pre-shared key, so an attacker who read the TGK off the wire could also forge a valid message MAC. Integrity was lost along with confidentiality. That aspect is tracked separately as GHSA-xq78-wvcv-hqvj.
Exploitability
A MIKEY message is normally distributed as an SDP a=key-mgmt:mikey attribute,
which in AES67 and SMPTE ST 2110 deployments is typically announced over SAP
multicast. A passive listener on the media network recovers the session key with
no active attack and no credentials.
RFC 3830 §4.2.3 permits NULL encryption only where "the underlying protocols can guarantee security", and warns to use it with caution. An SDP file or a SAP announcement is not such a channel.
The fix
Pre-shared key mode now follows RFC 3830 §3.1 as key transport: the initiator generates a random TGK, frames it as a Key data sub-payload (§6.13), and encrypts it with AES-CM (§4.2.3) under an encryption key and 112-bit salt derived from the pre-shared key (§4.1.4). The message MAC is keyed from the pre-shared key and verified before anything is decrypted.
This changes the wire format, so both ends of an exchange must be upgraded together. The incompatibility is silent: an old peer and a new peer complete the exchange without error and then derive different SRTP keys.
Workarounds
Use ephemeral Diffie-Hellman mode instead of pre-shared key mode, or carry the PSK-Init only over a channel that is already confidential and authenticated end to end.
| URL | Type | |
|---|---|---|
{
"affected": [
{
"database_specific": {
"categories": [
"crypto-failure"
],
"cvss": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
"informational": null
},
"ecosystem_specific": {
"affected_functions": null,
"affects": {
"arch": [],
"functions": [],
"os": []
}
},
"package": {
"ecosystem": "crates.io",
"name": "mykey",
"purl": "pkg:cargo/mykey"
},
"ranges": [
{
"events": [
{
"introduced": "0.0.0-0"
},
{
"fixed": "2.0.0"
}
],
"type": "SEMVER"
}
],
"versions": []
}
],
"aliases": [
"GHSA-fwjg-cm92-j3hj"
],
"database_specific": {
"license": "CC0-1.0"
},
"details": "`mykey` implements MIKEY (RFC 3830) for SRTP key exchange. Pre-shared key mode\ntransmitted the TEK Generation Key (TGK) in the clear.\n\n`MikeyMessage::new_psk_init` built its KEMAC payload with `EncAlg::Null` and\nplaced the TGK in `enc_data` verbatim. Anyone able to read a PSK-Init message\ntherefore recovers the TGK \u2014 and so the SRTP master key \u2014 **without knowing the\npre-shared key**.\n\nThe transmitted value was never even used by the receiver: `complete_psk`\nre-derived the TGK from the pre-shared key and ignored `enc_data` entirely. The\nfield was write-only; it provided nothing and disclosed everything.\n\nA second consequence: the message authentication key was derived from the TGK\nrather than from the pre-shared key, so an attacker who read the TGK off the wire\ncould also forge a valid message MAC. Integrity was lost along with\nconfidentiality. That aspect is tracked separately as GHSA-xq78-wvcv-hqvj.\n\n## Exploitability\n\nA MIKEY message is normally distributed as an SDP `a=key-mgmt:mikey` attribute,\nwhich in AES67 and SMPTE ST 2110 deployments is typically announced over SAP\nmulticast. A passive listener on the media network recovers the session key with\nno active attack and no credentials.\n\nRFC 3830 \u00a74.2.3 permits NULL encryption only where \"the underlying protocols can\nguarantee security\", and warns to use it with caution. An SDP file or a SAP\nannouncement is not such a channel.\n\n## The fix\n\nPre-shared key mode now follows RFC 3830 \u00a73.1 as key *transport*: the initiator\ngenerates a random TGK, frames it as a Key data sub-payload (\u00a76.13), and encrypts\nit with AES-CM (\u00a74.2.3) under an encryption key and 112-bit salt derived from the\npre-shared key (\u00a74.1.4). The message MAC is keyed from the pre-shared key and\nverified before anything is decrypted.\n\nThis changes the wire format, so both ends of an exchange must be upgraded\ntogether. The incompatibility is silent: an old peer and a new peer complete the\nexchange without error and then derive different SRTP keys.\n\n## Workarounds\n\nUse ephemeral Diffie-Hellman mode instead of pre-shared key mode, or carry the\nPSK-Init only over a channel that is already confidential and authenticated end\nto end.",
"id": "RUSTSEC-2026-0335",
"modified": "2026-10-12T08:58:45Z",
"published": "2026-10-09T12:00:00Z",
"references": [
{
"type": "PACKAGE",
"url": "https://crates.io/crates/mykey"
},
{
"type": "ADVISORY",
"url": "https://rustsec.org/advisories/RUSTSEC-2026-0335.html"
},
{
"type": "WEB",
"url": "https://github.com/waxspin/mykey/pull/25"
}
],
"related": [],
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
"type": "CVSS_V3"
}
],
"summary": "Pre-shared key mode transmits the TGK in cleartext, exposing the SRTP master key"
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
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- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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